Studies on the mechanism of action of pneumolysin on erythrocytes will be continued, the aim being identification of the aspect of target cell metabolism involved. The effects of various metabolites and inhibitors on cytolysin activity will be measured and the effect of lysin on membrane enzyme systems, such as adenylate cyclase, examined. Interaction between cytolysin and leucocytes will be studied by observation of: chemotactic action of pneumolysin and other components of pneumococcal cells; fixation of lysin to leucocytes; effects of pneumolysin on phagocytosis of intact leucocytes, on release of lysosomal enzymes from leucocyte granules, on leucocyte energy metabolism, on cell lysis and viability. The effects of various anti-inflammatory agents on these interactions will be assayed. Studies on the production and cellular location of the cytolysin produced by Pseudomonas aeruginosa will be performed by measuring lysin levels under varying cultural conditions. Interactions of purified cytolysin and leucocytes will also be examined.